This invention relates to mechanisms for providing adjustment of a work station, and more particularly to such mechanisms employing one or more lead screws and associated captive nuts to allow the displacement of one portion of the work station relative to another portion of the work station.
Adjustable work stations that are adaptable to variations in the sizes of various users are well known. Typical of such devices are drafting tables, easels, and the like. More recently, the wide-spread application of small computers and word processors has seen the introduction of computer work stations having independent adjustable supports for keyboard and display.
Many mechanisms have been used to permit the adjustment of the height of a work surface while still insuring the stability of the surface against loads. This latter requirement has frequently resulted in work stations which may be adjusted only with considerable effort, and then often only by discrete (and frequently less than optimal) amounts.
A solution which has been previously employed to permit continuous adjustment over a range of heights makes use of lead screws to provide the necessary mechanical advantage and ease of adjustment between elements of a structure. A screw having a length greater than the desired excursion is positioned on one element of the structure, with the screw's axis of rotation parallel to the desired direction of adjustment. A mating nut is affixed to the other element of the structure. Relative rotation of the nut and screw produces a relative linear displacement of the two elements. The present invention is directed toward such mechanisms.
A problem encountered with prior art devices incorporating such lead screws and captive nuts is the tendency of such mechanisms to bind unless they are made and assembled with careful attention to the dimensional tolerances and alignment of the various parts. Thus, the axes of the screw and of the structures constraining the travel of the moving component must generally be accurately parallel. In the event the motion is provided by a pair of parallel screws, they, too, must generally be accurately parallel. Such requirements for accurate parallelism impose critical limitations on component tolerances. This results in both greater manufacturing costs and higher maintenance requirements.
The effects of misalignment are further compounded by any eccentric loading of the nut. Any couple produced as a result of applying forces off the axis of the nut will tend to produce a binding torque. It will be appreciated that other design considerations (e.g., style, size, and the like) may preclude applying a balanced load to the nut.
Accordingly, it is an object of the present invention to provide a simple, easily fabricated adjustment means for adjustable work stations.
It is also an object of the present invention to provide a screw-driven adjustable work station which is relatively free of critical parts tolerances and assembly steps, yet is also relatively immune to binding during relative motion of the parts.
Yet another object of the present invention is to provide such an adjustment means which is easily maintained.
Still another object of the invention is to provide an adjustment mechanism comprising a lead screw and captive nut wherein the mechanism is relatively free of the deleterious effects of eccentric loading.